machine:

Config file section

Valid in machine config files YES
Valid in mode config files NO

The machine: section of your config is where you configure defails about the number of balls in your machine.

machine:
  balls_installed: 6
  min_balls: 3
This example is tested to be valid MPF config. However, it is not integration tested.
machine:
  balls_installed: 6
  min_balls: 3

Optional settings

The following sections are optional in the machine: section of your config. (If you don’t include them, the default will be used).

balls_installed:

Single value, type: integer. Default: 1

The (maximum) number of balls which should be installed in your machine.

min_balls:

Single value, type: integer. Default: 1

The minimum number of balls required to start a game. If less than min_balls are present MPF will refuse to stat a game.

It’s super annoying if you walk up to a pinball machine on location and can’t start a game because it’s missing a ball. So this setting lets you specify the minimum number of balls that need to be installed in order for a game to start. Note that it’s up to you to make sure your game code can handle fewer balls than you might be expecting.